The following compressor is known (e.g., patent document 1). In this compressor, a valve plate is arranged between a discharge chamber and a compression chamber. A discharge port, which extends through the valve plate, can communicate the discharge chamber and the compression chamber. A discharge reed valve, which is located in the discharge chamber, opens and closes the discharge port.
The discharge reed valve includes a fixed portion, which is fixed to a fixing surface that is a surface of the valve plate at a side facing the discharge chamber, an intermediate portion, which extends along a longitudinal direction of the discharge reed valve from the fixed portion and can be lifted, and a valve portion, which extends along the longitudinal direction of the discharge reed valve from the intermediate portion to open and close the discharge port. An annular groove that surrounds the entire circumference of the discharge port is arranged in the fixing surface. A portion of the fixing surface between the discharge port and the annular groove forms a valve seat surface that is flush with the portion of the fixing surface outward from the annular groove. In a state in which the discharge reed valve is closing the discharge port, an outer edge (distal part) of the valve portion extends beyond the valve seat surface in the longitudinal direction of the discharge reed valve.
In this type of compressor, it is ideal that the discharge port immediately open at the moment the difference between the pressure in the discharge chamber and the pressure in the compression chamber exceeds zero. However, when lubricating oil is present like in an actual machine, as shown in FIG. 25, an adhesive force S acts in a direction inhibiting the opening of a discharge reed valve 81. Thus, the discharge reed valve 81 does not open the discharge port 82 until a force F produced by the pressure difference prevails over the adhesive force S. In such a situation, a bore inner pressure (pressure in the compression chamber) is as shown in FIG. 26. Such a phenomenon in which the bore inner pressure becomes higher than the discharging pressure is referred to as over-compression and causes power loss.